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Journal Articles

Evaluation of the effect of composition and firing temperature on pore size distribution of ceramics by SANS measurement

Sugita, Tsuyoshi; Yoshida, Hirokazu*; Kodama, Hiroto*; Ishigaki, Toru*; Oba, Yojiro*

Journal of the Ceramic Society of Japan, 132(9), p.548 - 554, 2024/09

 Times Cited Count:1 Percentile:59.54(Materials Science, Ceramics)

Porosity plays an essential role in the performance of ceramics. In this study, the effects of clay composition and firing temperature on the pore size distribution of ceramics were evaluated by small-angle neutron scattering (SANS) measurements. Compared with quartz-rich pure Kasama clay, a mullite-rich Kasama clay blend had smaller pores after heat treatment. SANS measurements of D$$_{2}$$O-absorbed samples revealed that open pores with sizes ranging from tens of nanometers to about a micrometer contributed to the absorption of water. The closed and open pores coarsened and the total porosity decreased with increasing firing temperature.

Journal Articles

R&D status of digital technology on inverse estimation of radioactive source distributions and related source countermeasures; Fast Digital Twin Tech. in Decommissioning Field: 3D-ADRES-Indoor FrontEnd

Machida, Masahiko; Yamada, Susumu; Kim, M.; Tanaka, Satoshi*; Tobita, Yasuhiro*; Iwata, Ayako*; Aoki, Yuto; Aoki, Kazuhisa; Yanagisawa, Kenichi*; Yamaguchi, Takashi; et al.

RIST News, (70), p.3 - 22, 2024/09

Inside the Fukushima Daiichi Nuclear Power Plant (1F), there are many locations with high radiation levels due to contamination by radioactive materials that leaked from the reactor. These pose a significant obstacle to the smooth progress of decommissioning work. To help solve this issue, the Japan Atomic Energy Agency (JAEA), under a subsidy from the Ministry of Economy, Trade, and Industry's decommissioning and contaminated water management project, is conducting research and development on digital technologies to improve the radiation environment inside the decommissioning site. This project, titled "Development of Technology to Improve the Environment Inside Reactor Buildings (Enhancing Digital Technology for Environment and Source Distribution to Reduce Radiation Exposure)," began in April of FY 2023. In this project, the aim is to develop three interconnected systems: FrontEnd, Pro, and BackEnd. The FrontEnd system, based on the previously developed 3D-ADRES-Indoor (prototype) from FY 2021-2022, will be upgraded to a high-speed digital twin technology usable on-site. The Pro system will carry out detailed analysis in rooms such as the new office building at 1F, while the BackEnd system will serve as a database to centrally manage the collected and analyzed data. This report focuses on the FrontEnd system, which will be used on-site. After point cloud measurement, the system will quickly create a 3D mesh model, estimate the radiation source from dose rate measurements, and refine the position and intensity of the estimated source using recalculation techniques (re-observation instructions and re-estimation). The results of verification tests conducted on Unit 5 are also presented. Furthermore, the report briefly discusses the future research and development plans for this project.

Journal Articles

Effectiveness of fused LASSO for prediction of distribution of radioactive materials in reactor buildings

Yamada, Susumu; Yoshida, Toru*; Hasegawa, Yukihiro*; Machida, Masahiko

Proceedings of Waste Management Symposia 2024 (WM2024) (Internet), 15 Pages, 2024/03

In order to safely carry out the decommission of reactor buildings, it is extremely important to identify the radiation source distribution. It has been reported that when the structural model of the building is constructed by uniform cells, the source distribution can be estimated from the measured air dose rates by minimizing an evaluation function using the Least Absolute Shrinkage and Selection Operator (LASSO). Moreover, if cells are non-uniform, we can estimate the distribution using the fused LASSO which minimizes the evaluation function that takes account of the connectivity between the adjacent cells. However, when a group of some cells is considered disconnected from the surrounding ones due to the precision of the measured structural data, the concentration of the group can be singularly high. Therefore, in order to avoid the problem, we propose a new evaluation function that can prevent the singularity. We estimated the distribution for the test model using the proposed evaluation function and confirmed the validity of the function. Moreover, we succeeded in estimating the source distribution in the pool canal circulation system room in JMTR in the Japan Atomic Energy Agency by the fused LASSO for the new function more accurately than previous analysis.

Journal Articles

R&D of digital technology on inverse estimation of radioactive source distributions and related source countermeasures; R&D status of digital platform including 3D-ADRES-indoor

Machida, Masahiko; Yamada, Susumu; Kim, M.; Okumura, Masahiko; Miyamura, Hiroko; Shikaze, Yoshiaki; Sato, Tomoki*; Numata, Yoshiaki*; Tobita, Yasuhiro*; Yamaguchi, Takashi; et al.

RIST News, (69), p.2 - 18, 2023/09

The contamination of radioactive materials leaked from the reactor has resulted in numerous hot spots in the Fukushima Daiichi Nuclear Power Station (1F) building, posing obstacles to its decommissioning. In order to solve this problem, JAEA has conducted research and development of the digital technique for inverse estimation of radiation source distribution and countermeasures against the estimated source in virtual space for two years from 2021 based on the subsidy program "Project of Decommissioning and Contaminated Water Management" performed by the funds from the Ministry of Economy, Trade and Industry. In this article, we introduce the results of the project and the plan of the renewal project started in April 2023. For the former project, we report the derivative method for LASSO method considering the complex structure inside the building and the character of the source and show the result of the inverse estimation using the method in the real reactor building. Moreover, we explain the platform software "3D-ADRES-Indoor" which integrates these achievements. Finally, we introduce the plan of the latter project.

Journal Articles

Level structures of $$^{56,58}$$Ca cast doubt on a doubly magic $$^{60}$$Ca

Chen, S.*; Browne, F.*; Doornenbal, P.*; Lee, J.*; Obertelli, A.*; Tsunoda, Yusuke*; Otsuka, Takaharu*; Chazono, Yoshiki*; Hagen, G.*; Holt, J. D.*; et al.

Physics Letters B, 843, p.138025_1 - 138025_7, 2023/08

 Times Cited Count:6 Percentile:87.41(Astronomy & Astrophysics)

Gamma decays were observed in $$^{56}$$Ca and $$^{58}$$Ca following quasi-free one-proton knockout reactions from $$^{57,59}$$Sc. For $$^{56}$$Ca, a $$gamma$$ ray transition was measured to be 1456(12) keV, while for $$^{58}$$Ca an indication for a transition was observed at 1115(34) keV. Both transitions were tentatively assigned as the $$2^{+}_{1} rightarrow 0^{+}_{gs}$$ decays. A shell-model calculation in a wide model space with a marginally modified effective nucleon-nucleon interaction depicts excellent agreement with experiment for $$2^{+}_{1}$$ level energies, two-neutron separation energies, and reaction cross sections, corroborating the formation of a new nuclear shell above the N = 34 shell. Its constituents, the $$0_{f5/2}$$ and $$0_{g9/2}$$ orbitals, are almost degenerate. This degeneracy precludes the possibility for a doubly magic $$^{60}$$Ca and potentially drives the dripline of Ca isotopes to $$^{70}$$Ca or even beyond.

Journal Articles

Inverse estimation scheme of radioactive source distributions inside building rooms based on monitoring air dose rates using LASSO; Theory and demonstration

Shi, W.*; Machida, Masahiko; Yamada, Susumu; Yoshida, Toru*; Hasegawa, Yukihiro*; Okamoto, Koji*

Progress in Nuclear Energy, 162, p.104792_1 - 104792_19, 2023/08

 Times Cited Count:1 Percentile:34.39(Nuclear Science & Technology)

Predicting radioactive source distributions inside reactor building rooms based on monitoring air dose rates is one of the most essential steps towards decommissioning of nuclear power plants. However, the attempt is rather a difficult task, because it can be generally mapped onto mathematically ill-posed problem. Then, in order to successfully perform the inverse estimations on radioactive source distributions even in such ill-posed conditions, we suggest that a machine learning method, least absolute shrinkage and selection operator (LASSO) minimizing the loss function, $$||CP-Q||_2^2+lambda||_1$$ is a promising scheme. For the purpose of its feasibility demonstrations in real building rooms, we employ PHITS code to make LASSO input as the above matrix C connecting the radioactive source vector P defined on surface meshes of structural materials with the air dose rate vector Q measured at internal positions inside the rooms. We develop a mathematical criterion on the number of monitoring points to correctly predict source distributions based on the theory of Candes and Tao. Then, we confirm that LASSO actually shows extremely high possibility for source distribution reconstructions as far as the number of detection points satisfies our criterion. Moreover, we verify that radioactive hot spots can be truly reconstructed in an experiment setup. At last, we examine an influence factor like detector-source distance to enhance the predicting possibility in the inverse estimation. From the above demonstrations, we propose that LASSO scheme is a quite useful way to explore hot spots as seen in damaged nuclear power plants like Fukushima Daiichi nuclear power plants.

Journal Articles

LASSO reconstruction scheme for radioactive source distributions inside reactor building rooms with spectral information and multi-radionuclide contaminated situations

Shi, W.*; Machida, Masahiko; Yamada, Susumu; Yoshida, Toru*; Hasegawa, Yukihiro*; Okamoto, Koji*

Annals of Nuclear Energy, 184, p.109686_1 - 109686_12, 2023/05

 Times Cited Count:1 Percentile:34.39(Nuclear Science & Technology)

Journal Articles

Multiple mechanisms in proton-induced nucleon removal at $$sim$$100 MeV/nucleon

Pohl, T.*; Sun, Y. L.*; Obertelli, A.*; Lee, J.*; G$'o$mez-Ramos, M.*; Ogata, Kazuyuki*; Yoshida, Kazuki; Cai, B. S.*; Yuan, C. X.*; Brown, B. A.*; et al.

Physical Review Letters, 130(17), p.172501_1 - 172501_8, 2023/04

 Times Cited Count:11 Percentile:90.93(Physics, Multidisciplinary)

We report on the first proton-induced single proton- and neutron-removal reactions from the neutron deficient $$^{14}$$O nucleus with large Fermi-surface asymmetry at $$sim$$100 MeV/nucleon. Our results provide the first quantitative contributions of multiple reaction mechanisms including the quasifree knockout, inelastic scattering, and nucleon transfer processes. It is shown that the inelastic scattering and nucleon transfer, usually neglected at such energy regime, contribute about 50% and 30% to the loosely bound proton and deeply bound neutron removal, respectively.

Journal Articles

LASSO reconstruction scheme to predict radioactive source distributions inside reactor building rooms; Practical applications

Machida, Masahiko; Shi, W.*; Yamada, Susumu; Miyamura, Hiroko; Yoshida, Toru*; Hasegawa, Yukihiro*; Okamoto, Koji; Aoki, Yuto; Ito, Rintaro; Yamaguchi, Takashi; et al.

Proceedings of Waste Management Symposia 2023 (WM2023) (Internet), 11 Pages, 2023/02

Journal Articles

LASSO reconstruction scheme to predict radioactive source distributions inside reactor building rooms; Theory & demonstration

Shi, W.*; Machida, Masahiko; Yamada, Susumu; Yoshida, Toru*; Hasegawa, Yukihiro*; Okamoto, Koji*

Proceedings of Waste Management Symposia 2023 (WM2023) (Internet), 8 Pages, 2023/02

Journal Articles

"Southwestern" boundary of the $$N = 40$$ island of inversion; First study of low-lying bound excited states in $$^{59}$$V and $$^{61}$$V

Elekes, Z.*; Juh$'a$sz, M. M.*; Sohler, D.*; Sieja, K.*; Yoshida, Kazuki; Ogata, Kazuyuki*; Doornenbal, P.*; Obertelli, A.*; Achouri, N. L.*; Baba, Hidetada*; et al.

Physical Review C, 106(6), p.064321_1 - 064321_10, 2022/12

 Times Cited Count:2 Percentile:36.77(Physics, Nuclear)

The low-lying level structure of $$^{59}$$V and $$^{61}$$V was investigated for the first time. The neutron knockout reaction and inelastic proton scattering were applied for $$^{61}$$V while the neutron knock-out reaction provided the data for $$^{59}$$V. Four and five new transitions were determined for $$^{59}$$V and $$^{61}$$V, respectively. Based on the comparison to our shell-model calculations using the Lenzi-Nowacki-Poves-Sieja (LNPS) interaction, three of the observed $$gamma$$ rays for each isotope could be placed in the level scheme and assigned to the decay of the first 11/2$$^{-}$$ and 9/2$$^{-}$$ levels. The ($$p$$,$$p'$$) excitation cross sections for $$^{61}$$V were analyzed by the coupled-channels formalism assuming quadrupole plus hexadecapole deformations. Due to the role of the hexadecapole deformation, $$^{61}$$V could not be unambiguously placed on the island of inversion.

Journal Articles

Extended $$p_{3/2}$$ neutron orbital and the $$N = 32$$ shell closure in $$^{52}$$Ca

Enciu, M.*; Liu, H. N.*; Obertelli, A.*; Doornenbal, P.*; Nowacki, F.*; Ogata, Kazuyuki*; Poves, A.*; Yoshida, Kazuki; Achouri, N. L.*; Baba, Hidetada*; et al.

Physical Review Letters, 129(26), p.262501_1 - 262501_7, 2022/12

 Times Cited Count:15 Percentile:83.47(Physics, Multidisciplinary)

The one-neutron knockout from $$^{52}$$Ca was performed at $$sim$$230 MeV/nucleon combined with prompt $$gamma$$ spectroscopy. The momentum distributions corresponding to the removal of $$1f_{7/2}$$ and $$2p_{3/2}$$ neutrons were measured. The cross sections are consistent with a shell closure at the neutron number $$N = 32$$, found as strong as at $$N = 28$$ and $$N = 34$$ in Ca isotopes from the same observables. The analysis of the momentum distributions leads to a difference of the root-mean-square radii of the neutron $$1_{f7/2}$$ and $$2p_{3/2}$$ orbitals of 0.61(23) fm, in agreement with the modified-shell-model prediction of 0.7 fm suggesting that the large root-mean-square radius of the $$2p_{3/2}$$ orbital in neutron-rich Ca isotopes is responsible for the unexpected linear increase of the charge radius with the neutron number.

Journal Articles

R&D of digital technology on inverse estimation of radioactive source distributions and related source countermeasures; R&D status of digital platform including 3D-ADRES-indoor

Machida, Masahiko; Yamada, Susumu; Kim, M.; Okumura, Masahiko; Miyamura, Hiroko; Malins, A.; Shikaze, Yoshiaki; Sato, Tomoki*; Numata, Yoshiaki*; Tobita, Yasuhiro*; et al.

RIST News, (68), p.3 - 19, 2022/09

no abstracts in English

Journal Articles

Design and beam dynamics study of disk-loaded structure for muon LINAC

Sumi, Kazumichi*; Iijima, Toru*; Inami, Kenji*; Sue, Yuki*; Yotsuzuka, Mai*; Ego, Hiroyasu*; Otani, Masashi*; Saito, Naohito*; Mibe, Tsutomu*; Yoshida, Mitsuhiro*; et al.

Journal of Physics; Conference Series, p.012038_1 - 012038_6, 2022/07

The disk-loaded structures (DLS) in the muon LINAC are under development for the J-PARC muon g-2/EDM experiment. Four DLSs with an accelerating gradient of 20 MV/m take charge of muon acceleration from 40 MeV to 212 MeV, which corresponds to 70% to 94% of the speed of light. The quasi-constant gradient type TM01-2$$pi$$/3 mode DLSs with gradually varying disk spacing was designed and it was confirmed that the cumulative phase slip due to the mismatch between muon and phase velocity can be suppressed to less than 2 degrees at the frequency of 2592 MHz. In addition, the optimum synchronous phase and the lattice were investigated to satisfy the requirements of the total emittance less than 1.5$$pi$$ mm mrad and the momentum spread less than 0.1% in RMS.

Journal Articles

$$alpha$$-clustering in atomic nuclei from first principles with statistical learning and the Hoyle state character

Otsuka, Takaharu; Abe, Takashi*; Yoshida, Toru*; Tsunoda, Yusuke*; Shimizu, Noritaka*; Itagaki, Naoyuki*; Utsuno, Yutaka; Vary, J. P.*; Maris, P.*; Ueno, Hideki*

Nature Communications (Internet), 13, p.2234_1 - 2234_10, 2022/04

AA2021-0861.pdf:3.07MB

 Times Cited Count:39 Percentile:96.93(Multidisciplinary Sciences)

no abstracts in English

Journal Articles

A First glimpse at the shell structure beyond $$^{54}$$Ca; Spectroscopy of $$^{55}$$K, $$^{55}$$Ca, and $$^{57}$$Ca

Koiwai, Takuma*; Wimmer, K.*; Doornenbal, P.*; Obertelli, A.*; Barbieri, C.*; Duguet, T.*; Holt, J. D.*; Miyagi, Takayuki*; Navr$'a$til, P.*; Ogata, Kazuyuki*; et al.

Physics Letters B, 827, p.136953_1 - 136953_7, 2022/04

AA2021-0775.pdf:0.62MB

 Times Cited Count:7 Percentile:66.88(Astronomy & Astrophysics)

no abstracts in English

Journal Articles

Single-crystal structure analysis of non-deuterated triglycine sulfate by neutron diffraction at 20 and 298 K; A New disorder model for the 298 K structure

Terasawa, Yukana*; Ohara, Takashi; Sato, Sota*; Yoshida, Satoshi*; Asahi, Toru*

Acta Crystallographica Section E; Crystallographic Communications (Internet), 78(3), p.306 - 312, 2022/03

Journal Articles

Dissolution and precipitation behaviors of zircon under the atmospheric environment

Kitagaki, Toru; Yoshida, Kenta*; Liu, P.*; Shobu, Takahisa

npj Materials Degradation (Internet), 6(1), p.13_1 - 13_8, 2022/02

 Times Cited Count:1 Percentile:7.18(Materials Science, Multidisciplinary)

Journal Articles

PSTEP: Project for solar-terrestrial environment prediction

Kusano, Kanya*; Ichimoto, Kiyoshi*; Ishii, Mamoru*; Miyoshi, Yoshizumi*; Yoden, Shigeo*; Akiyoshi, Hideharu*; Asai, Ayumi*; Ebihara, Yusuke*; Fujiwara, Hitoshi*; Goto, Tadanori*; et al.

Earth, Planets and Space (Internet), 73(1), p.159_1 - 159_29, 2021/12

 Times Cited Count:7 Percentile:43.49(Geosciences, Multidisciplinary)

The PSTEP is a nationwide research collaboration in Japan and was conducted from April 2015 to March 2020, supported by a Grant-in-Aid for Scientific Research on Innovative Areas from the Ministry of Education, Culture, Sports, Science and Technology of Japan. It has made a significant progress in space weather research and operational forecasts, publishing over 500 refereed journal papers and organizing four international symposiums, various workshops and seminars, and summer school for graduate students at Rikubetsu in 2017. This paper is a summary report of the PSTEP and describes the major research achievements it produced.

Journal Articles

Present status and future perspective of R&D for 3D-ADRES (3-Dimensional Air Dose Rate Evaluation System); Evaluation scheme for air dose rate distributions in city and forest areas towards Fukushima's revitalization

Kim, M.; Malins, A.; Machida, Masahiko; Yoshimura, Kazuya; Saito, Kimiaki; Yoshida, Hiroko*; Yanagi, Hideaki*; Yoshida, Toru*; Hasegawa, Yukihiro*

RIST News, (67), p.3 - 15, 2021/09

no abstracts in English

189 (Records 1-20 displayed on this page)